A cellular communication system can support bi-directional communication for multiple users by sharing the available system resources. Cellular systems are different from broadcast systems that can mainly or only support unidirectional transmission from broadcast stations to users. Cellular systems are widely deployed to provide various communication services and may be multiple-access systems such as Code Division Multiple Access (CDMA) systems, Time Division Multiple Access (TDMA) systems, Frequency Division Multiple Access (FDMA) systems, Orthogonal FDMA (OFDMA) systems, Single-Carrier FDMA (SC-FDMA) systems, etc.
A cellular system may support broadcast, multicast, and unicast services. A broadcast service is a service that may be received by all users, e.g., news broadcast. A multicast service is a service that may be received by a group of users, e.g., a subscription video service. A unicast service is a service intended for a specific user, e.g., voice call. Group communications can be implemented using either unicast, broadcast, multicast or a combination of each. As the group becomes larger it is generally more efficient to use multicast services.